ALEXANDER VOK HUMBOLBT. 143 had lost.* Alexander has since fulfilled the noble duty towards the sacred memory of his brother by superintending his literary remains, and by publishing them regularly. Alexander soon again devoted himself exclusively to science, and a year rarely elapsed in which he did not cast a fertile glance into the kingdoms of nature, or did not discover some new treasure for science. Of his brother's manuscripts, he made his extensive re- searches on the Kawi4anguage into a subject for his o\Vn labours, for he had himself collected the materials for it, and its publication was therefore especially interesting for him. He lived on, working, and pro- ducing labours even in others, who often took a thought or single fact from Humboldt, developed it, and were led by it to important results. His Asiatic works occupied the principal part of his time, and necessitated an extensive correspondence with his friends in Russia and Paris; and besides this he had constantly to superintend and direct the labours which others devoted to his purposes. Besides this, lie was employed in the continuation of formerly-commenced works, and with his "Critical Investigations/'! In 1838 he published a politico- economical essay on the variations in the supply of * One passage of this letter says : ee I am. in the deepest grief, and &t such timea one thinks of those dearest to us, I feel a little re- lieved while writing to you. .% I remain quite desolate. I Ixope that I shall have the pleasure of being with you this year. . ." *f These critical investigations on the historical development of a geographical knowledge of the new world, and the progress of nauti- cal astronomy in the fifteenth and sixteenth century, appeared originally in French, and were published in German, by J. L. Ideler. They contain tho most important results of Humboldt's leisure hours during thirty years, and are the foundations of a history of Columbus, which he once intended to write. The work is in four divisions : the first treats of the causes wHefo prepared and led to the discovery of the new world—the second., of several facts more nearly relating to Christopher Columbus, and to Amorigo "Vespucci, and of the dates of several geographic discoveries •—the third, of the first maps of the new world, and of tlie time when the namo America was first commonly used—and the fourth, of the progrcBH of nautical astronomy and chart drawing in the fif- teenth and sixteenth centuries.